1. Technical Field
The present invention relates to a droplet discharge head, a droplet discharge device, a method for manufacturing the droplet discharge head and a method for manufacturing the droplet discharge device.
2. Related Art
As one of droplet discharge heads which discharge droplets, an ink-jet head mounted on an ink-jet storage device has been known. A typical ink-jet head includes a nozzle substrate in which a plurality of nozzle openings through which ink droplets are discharged is formed, a discharge chamber coupled to the nozzle substrate and which communicates with the nozzle openings in the nozzle substrate, and a cavity substrate in which an ink flow channel such as a reservoir is formed. Droplets are discharged through a selected nozzle opening when a driving part puts pressure on the discharge chamber. As for the discharge means, there are various methods such as an electrostatic method, a piezoelectric method using piezoelectric elements and a heating method using heater elements.
An ink-jet head having a plurality of raw of nozzles is required in order to increase a speed of printing and to realize a color printing. Moreover, nozzle density becomes highly concentrated and a nozzle length of the nozzle array becomes longer (or the number of nozzles per line is increasing) so that the numbers of actuators in an ink-jet head are recently increasing.
The ink-jet head has the reservoir that communicates with the discharge chamber. The reservoir is provided in each discharge chamber so that the pressure put on one of the discharge chambers is transmitted to the reservoir and the pressure affects the other discharge chamber and the nozzle openings which communicate with the discharge chamber especially when the nozzle openings are densely arranged. More specifically, when for example a positive pressure is put on the reservoir, an ink droplet can be discharged both from an unintended nozzle which is not driven and the intended nozzle (driven nozzle). When a negative pressure is put on the reservoir, the amount of the ink droplet discharged from the intended nozzle can become short from the appropriate amount and this deteriorates the printing quality.
JP-B-2-59769 (page 1, FIGS. 1-2) is a first example of related art. This patent document disclosed a technique which prevents such pressure interference among the nozzles. According to the example, an ink distributing plate having a diaphragm is provided on a member in which nozzles are formed.
However, the technique disclosed in the document makes it difficult to make the size of the ink-jet head smaller and thinner because the ink distributing plate is separately provided and coupled to the member in which the nozzles are formed.
JP-A-11-115179 (page 2, FIGS. 1-2) is a second example of related art. The second patent document disclosed an ink-jet head in which the diaphragm buffering the variation in the pressure of the reservoir is provided in the nozzle substrate.
However, the ink-jet head disclosed in the second example has the reservoir which is formed in the same substrate (cavity substrate) in which the discharge chamber is formed. In this case, from the perspective of securing sufficient volume of the reservoir, it is difficult to provide the diaphragm together with the reservoir in the same substrate. For this reason, the diaphragm is provided in a nozzle substrate according to the second example. However, a part that has a low strength is exposed in this configuration so that the diaphragm cannot be made much thinner. Moreover, a protection cover and the like will be required.